This invention relates to a printer, and more particularly to a low cost printer that is especially adapted for use in conjunction with electronic calculators, and the like.
As is well known, there is currently considerable interest in the field of low cost electronic calculators. In the case of the small pocket type calculators, the output typically comprises a visual readout. However, in the case of larger calculators, and particularly in the case of calculators intended for office use, it is considered preferable to provide a printed output, either alone or in combination with a visual readout. Thus, a need has arisen for a printer that is economical to manufacture, reliable in operation, and capable of long term, substantially maintenance free service.
The present invention comprises a printer that fulfills the foregoing requirements and is therefore particularly adapted for use in conjunction with low cost electronic calculators and similar applications. The printer is adapted for fabrication from a small number of relatively simple parts and thus is economical to manufacture. At the same time, the printer is adapted for long term, substantially maintenance free service. These combined characteristics of the printer of the present invention render its use highly advantageous over printers of the prior art.
In accordance with more specific aspects of the invention, a printer includes a continuously rotating print wheel having two rows of typefaces. Hammer structure is provided for actuating the typefaces to effect printing. The print wheel and the hammer structure are mounted on a carriage which functions to continuously move the print wheel and the hammer along a plurality of printing positions.
The printing positions are arranged in two groups with the left-hand group including nine printing positions and the right-hand group including two positions, the latter being separated from the left-hand group by a space. A cam includes a first portion corresponding to the first group of printing positions, a camming surface corresponding to the space separating the two groups of printing positions, and a second portion corresponding to the second group of printing positions. A cam follower engages the cam and functions to pivot the print wheel on the carriage mechanism between a first position wherein the first row of typefaces is aligned with the hammer mechanism, and a second position wherein the second row of typefaces is aligned with the hammer mechanism. The first row of typefaces includes the digits 0 through 9, inclusive, the comma (,) and the decimal (.) so that only numerical and punctuation entries are printed in the left-hand group of printing positions. The second row of typefaces includes all of the symbols, so that only symbols are printed in the right-hand group of printing positions.
The carriage mechanism includes a drive motor which rotates the drive pinion. A print wheel drive gear meshes with the drive pinion and is operatively connected to the print wheel to effect rotation thereof under the action of the drive motor. A reduction gear also meshes with the drive pinion and a pinion mounted on the reduction gear meshes with a rack to effect movement of the carriage mechanism under the action of the drive motor.
The print wheel comprises a plurality of radially extending arms each having a type font mounted thereon which includes a typeface in the first row and a typeface in the second row. The arms are nominally 30.degree. apart but are offset from this positioning so as to properly align the typefaces with the printing positions. Structure is provided for damping the movement of the arms following actuation thereof by the hammer structure.